We are developing/using 3d printed aluminium parts where I work (satellite manufacture) and have flown some smaller 3d printed aluminium components. The quality has improve massively with aluminium parts over the last few years. Airbus Civil Aircraft division have a goal of having an 80 metre by 80 metre printer (x & Y axis, not sure what Z was) by 2050 that can produce entire airframe sections according to one engineering publication. Not sure how quickly you could approve repairs to such a structure though. Some of the intricate structures I’ve seen as concept test pieces in our work would prove difficult to repair in a simple manner.